The present invention relates to cleansing blocks suitable for immersion in toilet tanks. The blocks are formulated to inhibit formation of toilet rings and surface stains.
Various cleansing blocks for use in toilet tanks and other water reservoirs are known. Such cleansing blocks typically contain a surfactant for cleaning, and often fillers, binders, colorants, extrusion aids and perfumes. They are designed to slowly release these materials into the toilet basin each time the toilet is flushed.
One particularly desirable form of such cleansing blocks are those that release chlorine compounds into the water supply to help clean and disinfect the toilet basin. See e.g. U.S. Pat. No. 5,336,427. The disclosure of this patent, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein. However, chlorinated cleansing blocks can have a relatively short usage life.
Creating longer life chlorinated cleansing blocks has been a significant challenge. Among other things, such cleansing blocks should not include materials which leave undesirable residues in the toilet bowl, which are environmentally unacceptable, which have unpleasant odors, or which have incompatibility with other components. For example, cellulose ether binders are known to prolong the life of some toilet cleansing blocks. See e.g. U.S. Pat. No. 4,269,723. However, they can be unstable in the presence of chlorine releasing compounds. Also, chlorine releasing agents can interfere with some dyes used in such blocks.
Thus, it can be seen that a need exists for an improved toilet chlorinated cleansing block.